1. A
person whose name you can't seem to remember.
2. A person whose name you
don't care about enough to try to remember.
3. A person whose name you can't seem to remember because said person is much like several other
people whose names you also can't remember.
4. A person who is simply unworthy of a name.
Example 1:
That
girl. With the hair and the eyes and the mouth and the
face. You know, Whoosit.
Example 2:
I know her, but I'm going to pretend that I forgot her name because I'm cool like that. "How's it going, whoosit?"
Example 3:
That
girl. With the hair and the eyes and the mouth and the face. The one that looks just like that other
girl with the hair and the eyes and the mouth and the face. You know, Whoosit.
Example 4:
"What did you say that guy's name was again?"
"Oh, him? He doesn't have one. He's just a whoosit."